Sitka Sound herring biomass much higher this year

The Alaska Dept. of Fish and Game has mapped 32 nautical miles of herring spawn through April 27, including 1.0 nmi of active spawn in Salisbury Sound. Spawn deposition surveys were conducted on April 7-11 and on April 24-25. Final results from this year’s stock assessment will not be available until November 2018, however, some general information can be derived from the data collected to date.

Nearly all spawning this year occurred along shorelines of Kruzof Island, Hayward Strait, and the Siginaka Islands. Very little spawning was observed in the islands near Sitka, which typically receive substantial spawn. The lack of spawn in the islands near Sitka and the lower than typical spawn mileage are unusual and have not been observed for many years. However, preliminary results of the spawn deposition survey revealed that although spawn mileage was approximately half that of 2017, the spawn extended nearly twice as far offshore, and egg density was higher.

In 2005 and 2008, a similar situation occurred where the spawn extended far offshore on Kruzof Island due to the very wide shelf of herring spawning habitat. Therefore, due to exceptional spawn along the Kruzof Island shoreline, the 2018 herring spawning biomass was much higher than was apparent from the spawn mileage alone.

The total harvest this season is 2,926 tons with an average o f 11.2 % mature roe. This harvest is 8,202 tons short of this season’s GHL of 11,128 tons. The department announced the season closure on the VH F radio at 11:00 a.m., April 3, 201 8. Multiple factors were considered in closing the fishery: The completion of the first spawn event with documented spawn totaling 13.3 nmi; the minimum size limit by processors (1 2 5 gram average) was higher this year than

past years and 60% of the forecast biomass was below the size necessary to satisfy market requirements; although herring were available, due to the higher market requirements, herring meeting these requirements were not found despite extensive vessel and aerial surveys conducted in the last several days prior to the closure . The decision to close the fishery was made in consultation with industry representatives.

In 2017, 62.3 nmi of herring spawn was mapped; peak spawn occurred on April 8 and the last spawn was observed on April 21. The 2017 model estimated post fishery biomass was 49,347 tons.

 

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